Winter worries

With freezing temperatures around the country we have had a lot of enquires about ponds freezing and how this will affect our amphibians and their spawn. Here we’ll try to answer some of your most frequently asked questions and put your mind at rest.

Spawn can be affected by cold weather. If a layer of ice forms over the surface of the spawn it may die, though the eggs at the bottom of the clump may survive. Sometimes icy weather can interrupt spawning, in which case a second batch of frogspawn may turn up in your pond once the cold weather subsides. Newt eggs and toad spawn tend to be more protected from frosts as they are laid slightly later in the year and deeper underwater.

Frogs may lie dormant at the bottom of ponds in winter. Occasionally, in particularly icy spells, frogs can die of 'winterkill', where toxic gases (released in the pond through natural decomposition of dead leaves) cannot escape from the pond due to the layer of ice. Though this can be upsetting to pond owners this phenomenon is largely natural and will only affect a very small percentage of the local frog population. Read more about winterkill on the Garden Wildlife Health website.

Amphibians can breathe through their skin. Providing that there is sufficient oxygen in the water, they can survive for long periods beneath the ice. A traditional solution has been to create a hole in the ice to allow gas exchange with the air. Recent research suggests that this may be ineffective, and growth of plants and green algae may be more helpful, as these oxygenate the water, even under ice. A hole in the ice probably won't make much difference to the oxygen level in the pond but it may help air breathing creatures which can swim to the surface for air (such as smooth newts). It will also give the birds somewhere to drink.

Clearing snow from the surface of a frozen pond may help, allowing more light to enter, hence increasing oxygen production from submerged plants and algae. Never pour hot water on to the ice or use chemicals or salt. Similarly, do not be tempted to smash the ice as this can damage pond liners and plants. The best way to create a hole in the ice is to leave a ball or other floating object in the pond which can be removed to leave a hole after it freezes.

Finally please do be very careful around frozen ponds. Although it looks solid the ice can be deceptively thin - it won’t hold much weight. Cleaning snow from the ice will make the pond more visible to anyone nearby.

Our native amphibians are well adapted for our weather conditions and although this very cold weather can be concerning they will undoubtedly muddle through and will soon be taking advantage of spring sunshine and spawning once more.